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From: "Marvin Kaye" <marv@lancaironline.net>
Subject: Re: Why a Lancair
To: lml
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Date: Sat, 22 Apr 2006 12:25:30 -0400
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Posted for "Mark & Lisa" <marknlisa@hometel.com>:

  Paul,
  
  Can you tell me more about the outer lip of the NACA duct?  Are you
  referring to the aft lip, or the sides?  My understanding is the sides edges
  must be sharp to induce the vortexes that create the airflow into the the
  duct.  Do I have this wrong?
  
  Regards,
  
  Mark Sletten
  Legacy FG N828LM
  http://www.legacyfgbuilder.com
  
  
  
   -----Original Message-----
   From: Paul Lipps [mailto:elippse@sbcglobal.net]
   Sent: Friday, April 21, 2006 20:57
   Subject: Why a Lancair
  
...snip...
  Don't steal cylinder cooling air from the
  upper plenum to feed the oil cooler. Feed it with a separate inlet with a
  diverging duct, then give it a converging duct and outlet pointing to the
  rear; don't just dump it into the area ahead of the firewall. Don't use the
  so-called "NACA" duct unless you understand its pressure recovery vs duct
  flow ratio. It's just one of three of the family of "submerged" ducts. Its
  proper name is divergent curved-wall submerged duct. There is also
  straight-wall divergent submerged duct and a parallel-wall submerged duct.
  Is the outer lip of your NACA duct sharp or is it rounded and shaped like an
  inverted leading edge? If it's sharp, it's wrong!
...snip...